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Friendicas DFRN Protocol —

* [Document with the DFRN specification](spec/dfrn2.pdf) * [Schema of the contact request process](spec/dfrn2_contact_request.png) * [Schema of the contact request confirmation](spec/dfrn2_contact_confirmation.png) * [Description of the message flow](help/Message-Flow)

ActivityStreams —

Friendica is using ActivityStreams in version 1.0 for its activities and object types. Additional types are used for non standard activities.

* [Link to the specification](http://activitystrea.ms/head/activity-schema.html) * [List of used ActivityStreams verbs and object types.](https://github.com/friendica/friendica/wiki/ActivityStreams)

Salmon —

Salmon is used as a message exchange protocol for replies and mentions.

* [Link to the protocol summary](http://www.salmon-protocol.org/salmon-protocol-summary)

Portable Contacts —

Portable Contacts is used for friends lists.

* [Link to the specification](https://web.archive.org/web/20160426223008/http://portablecontacts.net/draft-spec.html) (Link to archive.org)

pubsubhubbub —

pubsubhubbub is used for OStatus.

* [Link to the specification](https://pubsubhubbub.github.io/PubSubHubbub/pubsubhubbub-core-0.4.html)